10-km Squares Research Articles

The status of breeding Hen Harriers Circus cyaneus in the UK and Isle of Man in 2023

ABSTRACT Capsule The sixth national survey of breeding Hen Harriers in 2023 revealed a near-significant 20% increase in the UK and Isle of Man population since 2016, with variation between and within constituent countries. Aims To estimate the size of the breeding Hen Harrier population in the UK and Isle of Man, constituent countries, Scottish regions and the UK Special Protection Area (SPA) network for breeding Hen Harriers in 2023, and calculate population changes since 2016. Methods Surveys were conducted in all 10-km squares likely to be occupied by breeding birds in England, Northern Ireland, Wales and the Isle of Man, using standard methods. In Scotland, a stratified random selection of 10-km squares within the known breeding range was surveyed alongside squares selected by volunteers. Surveys were conducted in the UK in 2023 and Isle of Man in 2022. Results The UK and Isle of Man population was estimated at 691 territorial pairs (95% confidence limits, 593–802), a near-significant 20% increase since 2016. Populations increased by differing degrees in all countries and the Isle of Man, except in Northern Ireland where they declined. Scotland held 77% of the population with 529 (95% confidence limits, 431–640) pairs, with only tens of pairs in the other surveyed areas. Overall abundance within SPAs scarcely changed since 2016, but Scottish and Northern Irish SPAs held fewer pairs (−28% and −17%). As in 2016, most Hen Harriers were found on heather-dominated moorland. In Scotland, abundance declines on grouse-shooting moors continued between 2016 and 2023 (−23%), following a significant 67% decline between 2010 and 2016. Conclusion The 2023 survey showed a near-significant 20% increase in the UK and Isle of Man breeding Hen Harrier population since 2016. There was a substantial increase in England and moderate increases in Scotland, Wales and the Isle of Man, but a continuing decline in Northern Ireland. Breeding numbers within much of the SPA network in Scotland and Northern Ireland were below citation levels, with a more encouraging picture in England and particularly in Wales.

A new framework of spatial targeting for single-species conservation planning

Organisations acting to conserve and protect species across large spatial scales prioritise to optimise use of resources. Spatial conservation prioritization tools typically focus on identifying areas containing species groups of interest, with few tools used to identify the best areas for single-species conservation, in particular, to conserve currently widespread but declining species. A single-species prioritization framework, based on temporal and spatial patterns of occupancy and abundance, was developed to spatially prioritize conservation action for widespread species by identifying smaller areas to work within to achieve predefined conservation objectives. We demonstrate our approach for 29 widespread bird species in the UK, using breeding bird atlas data from two periods to define distribution, relative abundance and change in relative abundance. We selected occupied 10-km squares with abundance trends that matched species conservation objectives relating to maintaining or increasing population size or range, and then identified spatial clusters of squares for each objective using a Getis-Ord-Gi* or near neighbour analysis. For each species, the framework identified clusters of 20-km squares that enabled us to identify small areas in which species recovery action could be prioritized. Our approach identified a proportion of species’ ranges to prioritize for species recovery. This approach is a relatively quick process that can be used to inform single-species conservation for any taxa if sufficiently fine-scale occupancy and abundance information is available for two or more time periods. This is a relatively simple first step for planning single-species focussed conservation to help optimise resource use.

Status of the Hen Harrier Circus cyaneus in the UK and Isle of Man in 2016

ABSTRACTCapsule: The fifth UK and the Isle of Man survey of Hen Harrier in 2016 showed varying trends by country and region.Aim: To estimate the size of the breeding Hen Harrier population (with associated 95% confidence intervals) in the UK and Isle of Man, constituent countries and Scottish regions, in 2016 and calculate population change over the five surveys to date.Methods: Complete surveys were made of all 10-km squares likely to be occupied by breeding Hen Harriers in England, Wales, Northern Ireland and the Isle of Man, using standard methods developed for previous national surveys. In Scotland, self-selected 10-km squares were surveyed by volunteers and a stratified random selection of the remaining 10-km squares within the known breeding range was surveyed.Results: The UK and Isle of Man Hen Harrier population was estimated at 575 territorial pairs (95% confidence limits, 477–694), a non-significant decline of 13% since 2010 but a significant decline of 24% since 2004. Scotland held the majority (80%) of the population with 460 (359–573) territorial pairs. Elsewhere, 46 territorial pairs were recorded in Northern Ireland, 35 in Wales, 30 in the Isle of Man and four in England. Significant decreases were recorded in the number of pairs in Scotland using grouse moor (−57%) and young forest (−54%).Conclusion: The combined breeding population of Hen Harriers in the UK and Isle of Man has shown a non-significant decline between 2010 and 2016. There were notable decreases in England, Northern Ireland and Wales since 2010.

An updated distribution of Solidago × niederederi (Asteraceae) in Poland

Abstract In this paper, an updated map of the distribution of Solidago ×niederederi, a natural hybrid between S. canadensis and S. virgaurea, in Poland is presented using the ATPOL cartogram method. A compiled list of 55 localities of the hybrid within 40 cartogram units (10-km squares) is provided and its negative impact on S. virgaurea is highlighted.

Philip Arthur Dominic Hollom (1912-2014)

Philip Arthur Dominic Hollom (1912-2014)

The impact of changing habitat availability on population trends of woodland birds associated with early successional plantation woodland

Capsule Trends in young woodland availability influenced population trends and abundance of Tree Pipit and Lesser Redpoll, but not 10-km square occupancy.Aims To investigate whether changes in availability of young woodland could have driven population change, and trends in abundance and occupancy, of declining Tree Pipit and Lesser Redpoll populations in Britain.Methods Modelling approaches used annual population indices and woodland planting statistics. Abundance and occupancy change between two bird atlases were examined in relation to changes in woodland availability from two woodland inventories.Results English declines were strongly associated with decreases in young coniferous woodland availability and less strongly with increases in young broadleaved woodland. Abundance was related to the area of young woodland in corresponding 10-km squares. Young woodland availability declined between forest inventories and species occupancy maintained in 10-km squares with more young woodland; however squares that showed retention or increases in occupancy showed higher reductions in woodland.Conclusion We suggest declining availability of young coniferous woodland contributed to Tree Pipit and Lesser Redpoll population trends in England. Although likely to be the case in Scotland and Wales, the lack of sufficient temporal data inhibited our ability to test this properly. This work suggests that woodland availability was not the primary driver of Tree Pipit or Lesser Redpoll population trends.

Generating population estimates for common and widespread breeding birds in Ireland

Capsule Population estimates for 51 common breeding birds, totalling 62 million individuals, were estimated for Ireland.Aims To generate robust population estimates for common and widespread breeding birds across Ireland.Methods Densities were generated for common breeding birds using data from annual bird monitoring surveys using count data for all years between 2006 and 2010 inclusive. Bird atlas data were then used to (1) quantify the distribution of each species (10-km squares), and (2) generate an estimate of proportion occurrence of each species within each square. The total number of birds of each species was generated by multiplying proportion occupancy by the total area of the 10-km square and by the mean regional density generated from the bird monitoring data, and by summing the estimates of squares.Results Almost 62 million individuals of 51 common breeding birds were estimated. Wren Troglodytes troglodytes, with an estimate of more than 6 million individuals, contributed 10% of the total birds recorded. Swallow Hirundo rustica and Robin Erithacus rubecula were the next most numerous, at 5.8 and 5.4 million individuals. A total of 15 species were estimated at more than one million individuals each.Conclusion The estimates of detected individuals generated are based on best available information and analyses to date. Incorporating the bird atlas data permits vastly improved estimates by providing better informed distribution range across which the regional densities were extrapolated. However, estimation of densities and population sizes based on data from annual monitoring surveys alone is limited to species with widespread distributions because of the relatively low coverage and limited detectability of scarce species by this methodology.

The status of the Hen Harrier, Circus cyaneus, in the UK and Isle of Man in 2010

Capsule The fourth national survey of Hen Harrier showed that the population in the UK and the Isle of Man declined significantly between 2004 and 2010.Aim To estimate the size of the breeding Hen Harrier population (with associated 95% confidence intervals) in the UK and Isle of Man, constituent countries and Scottish regions, in 2010 and calculate population change since previous surveys in 1998 and 2004.Methods Complete surveys were made of 10-km squares likely to be occupied by breeding Hen Harriers in England, Wales, Northern Ireland and the Isle of Man, using standard methods developed for previous national surveys. In Scotland, a ‘census’ area was non-randomly selected for survey by volunteers, and randomly selected squares were surveyed in two strata covering the rest of the known range.Results The UK and Isle of Man Hen Harrier population was estimated at 662 territorial pairs (95% confidence interval (CI): 576–770), a significant decline of 18% since 2004. Scotland holds the bulk (76%) of the population (505 territorial pairs; 95% CI: 417–612), with smaller numbers in Northern Ireland (59 pairs), Wales (57 pairs), the Isle of Man (29 pairs) and England (12 pairs). Declines of 49% and 20% were observed in the Isle of Man and in Scotland, respectively, whereas the Welsh population increased by 33%. A significant decrease was recorded in numbers of pairs using young and mature plantation forest in Scotland.Conclusion The breeding population of Hen Harriers in the UK and Isle of Man declined between 2004 and 2010. Notable decreases in Scotland and the Isle of Man may be related to habitat change and illegal persecution. Illegal persecution continues to limit the population size of harriers in England to very low levels.

Species distribution, ecology, abundance, body size and phylogeny originate interrelated rarity patterns at regional scale

The most pervasive macroecological patterns concern (1) the frequency distribution of range size, (2) the relationship between range size and species abundance and (3) the effect of body size on range size. We investigated these patterns at a regional scale using the tenebrionid beetles of Latium (Central Italy). For this, we calculated geographical range size (no. of 10-km square cells), ecological tolerance (no. of phytoclimatic units) and abundance (no. of sampled individuals) using a large database containing 3561 georeferenced records for 84 native species. For each species, we also calculated body mass and its ‘phylogenetic diversity’ on the basis of cladistic relationships. Frequency distribution of range size followed a log-normal distribution as found in many other animal groups. However, a log-normal distribution accommodated well the frequency distribution of ecological tolerance, a so far unexplored issue. Range size was correlated with abundance and ecological tolerance, thus supporting the hypothesis that a positive correlation between distribution and abundance is a reflection of interspecific differences in ecological specialization. Larger species tended to have larger ranges and broader ecological tolerance. However, contrary to what known in most vertebrates, not only small-sized, but also many medium-to-large-sized species exhibited great variability in their range size, probably because tenebrionids are not so strictly influenced by body size constraints (e.g. home ranges) as vertebrates. Moreover, in contrast to other animals, tenebrionid body size does not influence species abundances, probably because these detritivorous animals are not strongly regulated by competition. Finally, contrary to the assumption that rare species should be mainly found among lineages that split from basal nodes, rarity of a tenebrionid species was not influenced by the phylogenetic position of its tribe. However, lineages that split from more basal nodes had lower variability in terms of species geographical distribution, ecological tolerance and abundance, which suggests that lineages that split from more basal nodes are not only morphologically conservative but also tend to have an ecological ‘inertia’.

Detecting change in the status and habitat of Hinde's BabblerTurdoides hindei: 2000 to 2011

Department of Zoology, National Museums of Kenya,PO Box 40658-00100, Nairobi, KenyaBACKGROUNDThe globally Vulnerable Kenyan endemic Hinde’s Bab-bler Turdoides hindei has its stronghold in the foothills ofMt Kenya and the Aberdares, where it is associatedmainly with patches of scrub and riverine thicket (Statt-ersfield et al. 1998, Njoroge & Bennun 2000, BirdLifeInternational 2012). A decline in its known range, firstdescribed in the 1970s, was attributed to scrub clearancefor cultivation, perhaps compounded in some areas byhuman disturbance and hunting (Plumb 1979, Njorogeet al. 1998). Surveys in 1994 and 2000–2001 showedthat the species was much less abundant within pro-tected areas than in fertile, densely populated farmland,offering limited scope for conservation through furthersite designation (Shaw & Musina 2003).The global range of Hinde’s Babbler lies predomi-nantly within the catchments of the upper Tana River,with outlying populations in Meru District, Machakos,Kitui and Nziu (Shaw et al. 2003). By 2001 the specieswas known from just seven main areas, and was thoughtto have a global population of c. 1500–5600 birds.Although scrub clearance has impacted on the species’range and population, its effect may have been partlymitigated by the spread of the exotic invasive Lantanacamara, which provides scrub cover in areas previouslycleared of native shrubs, enabling the Babbler to persistin, and possibly to re-colonize, intensively farmed land(Njoroge & Bennun 2000).Like most members of its genus, Hinde’s Babblerbreeds cooperatively, groups typically comprising threeto four adults (range 1–8), often accompanied by one ortwo juveniles (Njoroge & Mutinda 1996, Shaw & Musi-na 2003). Some groups include individuals with exten-sive light feathering on the chest, head and back,sometimes distributed asymmetrically, a trait interpretedby Plumb (1979) as possible evidence of inbreeding.In 2011 we reassessed the global range of Hinde’sBabbler and resurveyed three sites previously surveyedin 2000–2001, to determine whether changes hadoccurred in its known range, abundance, demography orhabitat over the intervening decade. To determine therelationship between plumage type, population densityand breeding success we assigned a plumage score to allindividuals seen sufficiently clearly, noting their age classand group composition.GLOBAL RANGEChanges in Hinde’s Babbler’s global range were estimatedfrom the number of occupied 10 9 10-km squares (itsArea of Occupancy) and from the number of squaresbounded by these known sites (its Extent of Occurrence).Three time periods were compared: 1900–1970,1971–1990 and 1991–2011. Since its discovery in 1900,Hinde’s Babbler has been recorded in 53 squares, indicat-ing an Area of Occupancy of c. 5300 km

Breeding status of Merlins Falco columbarius in the UK in 2008

Capsule The third national Merlin survey estimated a UK population of 1162 breeding pairs (95% CI: 891–1462). Aims To estimate the number of breeding Merlins (with associated 95% confidence intervals) in the UK and the four countries (Scotland, England, Wales and Northern Ireland), and to compare these with the relevant estimates from the 1993–94 Merlin survey. In addition, to calculate estimates of change for several regional populations with complete survey coverage during both national surveys. Methods A subset of 10-km squares (Raptor Study Group squares and randomly sampled squares) was surveyed across the breeding distribution of Merlins in the UK using standardised methods devised during the 1993–94 national survey. Results The population estimate for Merlins in the UK was 1162 breeding pairs, and in Britain was 1128 pairs (95% CI: 849–1427), which although 13% lower, was not significantly different from the British estimate of the 1993–94 survey. Scotland held the bulk (733 pairs) of the UK Merlin population, and smaller numbers of 301 pairs, 94 pairs and 32 pairs were estimated for England, Wales and Northern Ireland, respectively. The population estimate for Wales may have been biased upwards by low coverage in the south of the country. Marked declines were noted in several regional Merlin populations, particularly in areas of northern England. Conclusions The 2008 Merlin survey suggests that the population in Britain has remained relatively stable since 1993–94, but with local declines, particularly in northern England. Currently, little is known about important drivers of regional population change in Merlins, but changes in land-use, prey populations and climate are likely to be important factors.

The status and distribution of summering Greylag Geese Anser anser in Scotland, 2008–09

Capsule Summering Greylag Geese Anser anser are increasing in number and expanding their range in Scotland. Aims During the summers of 2008 and 2009, extensive surveys of Greylag Geese in Scotland were undertaken to update the current distribution and population estimates, as well as estimate breeding success. Methods Checks of known moult-sites were combined with a random stratified sample of lochs to the south and east of the Great Glen (the ‘re-established population’ area). Sample lochs were selected on the basis of altitude, the proportional areas of woodland and water cover and previous summer records of Greylag Geese within the 10-km squares in which the lochs were located. To the north and west of the Great Glen (the ‘northwest Scotland’ population area), comprehensive post-breeding counts of feeding areas were undertaken in late August. Results Combined results from 2008 and 2009 suggest an estimated 47 405 (range 44 059–51 763) Greylag Geese in Scotland. Since 1989, Greylag Geese encountered to the south and east of the Great Glen (derived from re-established birds) have increased at an annual rate of about 9.7% per annum and, since 1997, those in northwest Scotland have increased at an annual rate of about 11.7% per annum. It is estimated that the total number of Greylag Geese summering in Britain is about 84 500 birds. In 2008, overall breeding success was 24.1% young in the late summer population, which probably more than compensates for natural and shooting mortality. Conclusion There is no indication of a decline in the rate of increase of Greylag Geese in Scotland and the species is expected to continue to increase in abundance and distribution.

Modelling distributional trends to inform conservation strategies for an endangered species

Aim Species loss has increased significantly over the last 1000 years and is ultimately attributed to the direct and indirect consequences of increased human population growth across the planet. A growing number of species are becoming endangered and require human intervention to prevent their local extirpation or complete extinction. Management strategies aimed at mitigating a species loss can benefit greatly from empirical approaches that indicate the rate of decline of a species providing objective information on the need for immediate conservation actions, e.g. captive breeding; however, this is rarely employed. The current study used a novel method to examine the distributional trends of a model endangered species, the freshwater pearl mussel, Margaritifera margaritifera (L.). Location United Kingdom and Republic of Ireland. Methods Using species presence data within 10-km grid squares since records began three-parameter logistic regression curves were fitted to extrapolate an estimated date of regional extinction. Results This study has shown that freshwater pearl mussel distribution has contracted since known historical records and outlier populations were lost first. Within the United Kingdom and Republic of Ireland, distribution loss has been greatest in Scotland, Northern Ireland, Wales and England, respectively, with the Republic of Ireland containing the highest relative proportion of M. margaritifera distribution, in 1998. Main conclusions This study provides empirical evidence that this species could become extinct throughout countries within the United Kingdom within 170 years under the current trends and emphasizes that regionally specific management strategies need to be implemented to prevent extirpation of this species.

Assessing range re-expansion and recolonization of human-impacted landscapes by threatened species: a case study of the otter (Lutra lutra) in Italy

Detecting and understanding recoveries of threatened species from past and recent presence/absence data is essential to improving conservation efforts. However, false positive trends may be reported because of false absences in past data, therefore appropriate testing is needed. We tested an expansion/recolonization of the otter (Lutra lutra) populations in Italy from a fragmented distribution outlined in the 1984-1985 period by using Monte Carlo simulations. Land-use changes, human depopulation and decrease in influence of anthropogenic features were investigated as potential drivers of recolonization by using GIS modeling. A survey of the entire Italian range of the otter, conducted in 2002-2004, recorded a 2.2-fold increase in the proportion of occupied 10-km squares and 49 local colonizations. The range size and proportion of urban land-use in the 1984-1985 distribution were smaller (P < 0.05) than those derived from simulated surveys based on 49 random false absences versus colonization events. The distribution range expanded southward and nearly reached the southern margins of the peninsula. Recolonization of moderately urbanized landscapes was not accompanied by human depopulation. According to partial logistic regressions, the pure effect of urban land proportion and industry proximity on otter occurrence probability declined by about 48%, suggesting a decreased impact on the stream habitat. Conversely, natural factors, increased in importance by about 116%. The absence of a significant northward expansion in the 20 year period suggests that northward habitat restoration should be planned to encourage further recolonization. On the other hand, potential urban threats in the newly occupied landscapes should be controlled.

Mapping wildlife: integrating stakeholder knowledge with modelled patterns of deer abundance by using participatory GIS

Context. Some species that are perceived by certain stakeholders as a valuable resource can also cause ecological or economic damage, leading to contrasting management objectives and subsequent conflict between stakeholder groups. There is increasing recognition that the integration of stakeholder knowledge with formal scientific data can enhance the information available for use in management. This is especially true where scientific understanding is incomplete, as is frequently the case for wide-ranging species, which can be difficult to monitor directly at the landscape scale. Aims. The aim of the research was to incorporate stakeholder knowledge with data derived from formal quantitative models to modify predictions of wildlife distribution and abundance, using wild deer in the UK as an example. Methods. We use selected predictor variables from a deer–vehicle collision model to estimate deer densities at the 10-km square level throughout the East of England. With these predictions as a baseline, we illustrate the use of participatory GIS as a methodological framework for enabling stakeholder participation in the refinement of landscape-scale deer abundance maps. Key results. Stakeholder participation resulted in modifications to modelled abundance patterns for all wild deer species present in the East of England, although the modifications were minor and there was a high degree of consistency among stakeholders in the adjustments made. For muntjac, roe and fallow deer, the majority of stakeholder changes represented an increase in density, suggesting that populations of these species are increasing in the region. Conclusions. Our results show that participatory GIS is a useful technique for enabling stakeholders to contribute to incomplete scientific knowledge, especially where up-to-date species distribution and abundance data are needed to inform wildlife research and management. Implications. The results of the present study will serve as a valuable information base for future research on deer management in the region. The flexibility of the approach makes it applicable to a range of species at different spatial scales and other wildlife conflict issues. These may include the management of invasive species or the conservation of threatened species, where accurate spatial data and enhanced community involvement are necessary in order to facilitate effective management.

Are native bluebells ( Hyacinthoides non-scripta) at risk from alien congenerics? Evidence from distributions and co-occurrence in Scotland

The UK has the highest density of the worldwide distribution of its native bluebell, Hyacinthoides non-scripta (Liliaceae), and the prevalence of alien bluebells (hybrids or ‘Spanish’) has been interpreted as an urgent threat. To assess the potential for competitive and hybridising interactions between natives and alien taxa in the UK, we quantified abundance and co-occurrence in south-central Scotland in relation to physical variables, land cover, and habitat types. To do this we tested the influence of explanatory variables on incidence rates, densities and group sizes at three spatial scales (10 km, 1 km, and records) in selected 10-km squares. We found that (1) natives were nearly 99% of all bluebells recorded, (2) aliens were encountered more frequently than natives though in much smaller maximum numbers per group, (3) increasing rainfall was associated with increasing native and decreasing alien densities, (4) the presence of aliens related to variables correlated with human density, and (5) there was little evidence for habitat exclusivity. Mixed groups accounted for 10% of natives recorded, and over 40% of natives grew within about one kilometre of aliens. These distributions suggest that a high proportion of natives lie within range of potential gene flow via insect pollinators.

Status of the Hen Harrier Circus cyaneus in the UK and Isle of Man in 2004, and a comparison with the 1988/89 and 1998 surveys

Capsule The population of breeding Hen Harriers in the UK and Isle of Man increased between 1998 and 2004, although country and regional trends differed. Aims To estimate the size of the UK and Isle of Man Hen Harrier breeding population in 2004, and to compare this with previous estimates made in 1988/89 and 1998. Methods Surveys were carried out in core and a stratified random sample of 10-km squares throughout the known range, using the same methods as in the 1988/89 and 1998 national surveys. Results There were an estimated 806 territorial pairs in the UK and Isle of Man in 2004, a significant 41% increase from the 1998 estimate of 570 pairs. Increases were found throughout, with the exception of south and east Scotland and England, where numbers decreased. Scotland held 79% of the UK and Isle of Man breeding population in 2004, and 10% of Scottish pairs were associated with non-moorland habitats, such as mature conifer plantations and scrub/brash. Conclusions There was a substantial increase in the breeding population in most regions of the UK and Isle of Man between 1998 and 2004, possibly aided by increased use of non-moorland habitats. However, populations declined in upland areas of southern and eastern Scotland and northern England. Continuing illegal persecution arising from perceived conflicts between breeding Hen Harriers and driven grouse shooting may be a major cause of these regional declines.

Effects of land cover and climate on species richness of butterflies in boreal agricultural landscapes

This study examined how species richness of butterflies with differing population trends is affected by land cover and climate. Generalized linear models (GLM) with land cover, climate and geographical location as explanatory variables were constructed to explain variation in species richness of declining, stable and increasing butterflies in 10-km squares in Finland. The largest part of explained variation in species richness of all the three butterfly trend categories was related to spatially structured climate variables and pure geographical location. However, the relative importance of climate and land cover differed between the butterfly categories. Pure and spatially structured climate variables explained two-fold more variation in species richness in increasing butterflies than in stable and declining butterflies. On the other hand, pure and spatially structured land cover variables explained 2.5–6 times more variation in species richness in declining butterflies than in stable and increasing butterflies. Land cover variables differed in their effects on the species richness of the three trend categories: the amount of grassland had the greatest positive effect on the number of declining species, whereas the amount of forest was the most important land cover variable for species richness of stable butterflies and arable land and field-forest mosaic for species richness of increasing butterflies. The results suggest that habitat availability has the greatest effect on the trends of declining butterfly species, and climate in concert with habitat availability on the trends of increasing species.

Status and distribution of European Nightjars Caprimulgus europaeus in the UK in 2004

Capsule The population of Nightjars in the UK increased by over 36% between 1992 and 2004. Aims To determine the population size and distribution of Nightjars in the UK and examine associations with forestry and heathland habitat features. Methods A volunteer survey was supported by professional cover in remote parts of Wales, and areas of Dorset and lowland Scotland. Two visits to allocated 1-km squares were made between late May and mid-July. Each surveyor recorded the locations of calling males onto maps and the occurrence of habitat categories within 50 m of each Nightjar registration. Results Observers surveyed 3264 1-km squares in 2004 and, on average, 78% of the target habitat (90% in southern England). The total number of males counted was 4131 (range 3850–4414), adjusted to 4606 (95% CL ± 913) to account for unsurveyed habitat. The adjusted total represented a 36% increase in 12 years. Nightjars were recorded in 275 10-km squares in 2004, a 2.6% increase since 1992. However, there was evidence of population decline and range contractions in northwest Britain, including north Wales, northwest England and in Scotland. In 2004, 57% of Nightjars were associated with forest plantations (similar to 1992) and 59% with heathland (slightly higher than in 1992). Conclusion National objectives for Nightjar conservation (UK Biodiversity Action Plan: UKBAP) were reached in respect of population size and stability, but the target for a 5% range increase by 2003 was not met. The continued increase in the national population is probably attributable to habitat protection, management and restoration of heathlands, and the continued availability of clear-fell/young plantations in conifer forests. Management and/or protection/restoration/re-creation of these key habitats remains critical for the long-term objectives of UKBAP. The issue of providing foraging habitats, perhaps via agri-environment schemes, is also raised.

Partial recovery of the population of Corncrakes Crex crex in Britain, 1993–2004

Capsule Singing male Corncrakes increased more than two-fold over the study period. Aim To provide updated counts of the number and distribution of singing male Corncrakes in Britain and describe the implementation of schemes in which land management was modified to benefit Corncrakes. Methods Annual surveys of singing Corncrakes in the core of the range in Britain were undertaken between 1993 and 2004 and the total population of the species throughout Britain was assessed in 2003. Annual information on the extent and location of the various conservation management schemes was obtained from the authorities that administer them. Results Following a long-term decline, the count of Corncrakes in the core of the species' British range increased in ten of the 11 years since 1993. A survey of the core of the range in 2004 located 1040 singing males, a 2.3-fold increase on the 446 singing males located in the same area in 1993. A full survey of Britain and the Isle of Man in 2003 located 832 singing males in 81 10-km National Grid squares. This compares with 589 birds in 93 squares in the last full survey in 1998, and 480 birds in 83 squares in 1993. During 1993–2003, more than 70% of Corncrakes in the core area occurred in 1-km National Grid squares in which conservation schemes were implemented. For males in squares with some conservation management, the average area of managed land to which each bird potentially had exclusive access was about 5 hectares. About half of the tall grass present in 1-km squares occupied by Corncrakes was included in schemes intended to modify mowing or grazing to reduce losses of nests and chicks. Conclusion There has been a partial recovery of the population of Corncrakes in Britain since 1993, reversing a decline that began in the late 19th and early 20th centuries. However, the geographical range of the species, measured as occupied 10-km grid squares, has not increased. The recovery occurred during a period in which a significant area of land, to which the majority of Corncrakes had access, was entered into conservation management schemes intended to benefit the species. Estimated changes in breeding productivity likely to be associated with changes in grass-mowing management on the observed scale were approximately sufficient to account for the observed change in population trend.